setFloat method

void setFloat(
  1. int index,
  2. double value

Sets the float uniform at index to value.

All uniforms defined in a fragment shader that are not samplers must be set through this method. This includes floats and vec2, vec3, and vec4. The correct index for each uniform is determined by the order of the uniforms as defined in the fragment program, ignoring any samplers. For data types that are composed of multiple floats such as a vec4, more than one call to setFloat is required.

For example, given the following uniforms in a fragment program:

uniform float uScale;
uniform sampler2D uTexture;
uniform vec2 uMagnitude;
uniform vec4 uColor;

Then the corresponding Dart code to correctly initialize these uniforms is:

void updateShader(ui.FragmentShader shader, Color color, ui.Image image) {
  shader.setFloat(0, 23);  // uScale
  shader.setFloat(1, 114); // uMagnitude x
  shader.setFloat(2, 83);  // uMagnitude y

  // Convert color to premultiplied opacity.
  shader.setFloat(3, / 255 * color.opacity);   // uColor r
  shader.setFloat(4, / 255 * color.opacity); // uColor g
  shader.setFloat(5, / 255 * color.opacity);  // uColor b
  shader.setFloat(6, color.opacity);                     // uColor a

  // initialize sampler uniform.
  shader.setImageSampler(0, image);

Note how the indexes used does not count the sampler2D uniform. This uniform will be set separately with setImageSampler, with the index starting over at 0.

Any float uniforms that are left uninitialized will default to 0.


void setFloat(int index, double value) {
  assert(!debugDisposed, 'Tried to accesss uniforms on a disposed Shader: $this');
  _floats[index] = value;